Re: Beginner's questions

[Matthew Heaney <matthew_heaney@acm.org>]

marcoschmidt@geocities.com (Marco Schmidt) writes:

> 1) I couldn't find out how to use bitwise operations "and" and "or"
> (which would be "and" / "or" in Pascal and "&" / "|" in C). Do I have
> to include a certain package?

Those operations predefined for all modular types.  Were you using an
integer type?


> 2) I want to use a fixed-size array of constant strings to store some
> names which do not all have the same length, but no name is longer
> than 20 characters. My approach looks like this:
> 
>   type t_my_array is array(0..17) of String;
> 
>   names : constant t_my_array := ("string 1", "string 2", ...,
>     "string 18");
> 
> The compiler doesn't like this (unconstrained element type). If I
> replace String with String(0..19), it is compiled, but a runtime error
> is raised. How should I do it?


You could use an instantation of
Ada.Strings.Bounded.Generic_Bounded_Length.

Or you could use Ada.Strings.Unbounded.

Or you could use a discriminated record:

  subtype Name_Length_Range is Natural range 0 .. 20;

  type Name_Buffer (Length : Name_Length_Range := 0) is
    record
        Name : String (1 .. Length);
    end record;

  function "+" (R : String) return Name_Buffer is
  begin
    return (R'length, R);
  end;

  type Name_Array is array (Positive range <>) of Name_Buffer;

  Names : Name_Array :=
    (+"Heckle",
     +"Jeckle",
     +"Marvelous",
     +"Magpies",
     +"Let's have some fun",
     +"With name arrays");